1. Field of the Invention
The present invention relates to generally to the control and extinguishment of fires, and more particularly, to the control and extinguishment of compartment fires.
2. Description of the Background Art
Compartment fires, unlike open air fires, have limited access to the outside environment. This limited access restricts the transfer of heat and fumes with the environment. Therefore, compartment fires are often extremely hot and may quickly contaminate the affected compartment with dangerous levels of toxic fumes. Additionally, compartment fires have the potential to spread quickly throughout the compartment. Moreover, the restricted venting of a compartment to the outside, while it allows sufficient oxygen to maintain the fire, may prevent combustible fuel in the compartment from cooling sufficiently quickly to prevent post suppression reignition. Thus, compartment fires must be rapidly and thoroughly extinguished to minimize loss of life and/or property.
Many compartments made for housing combustibles include a fire suppression system. The most widely accepted fire suppression system for fires uses fluorinated bromohydrocarbons such as Halon.TM.. Halon.TM. performs exceptionally well at fully extinguishing fires and preventing post suppression reignition, with few toxic byproducts being generated during fire suppression. Nevertheless, the manufacture of fluorinated bromohydrocarbons has been banned because of the threat they pose to the ozone layer. Thus, other gaseous fire suppression agents have been substituted for Halon.TM..
Generally, these other gaseous fire suppression agents have lacked the qualities of Halon.TM.. Compared with Halon.TM., many exhibit poor fire suppression efficiency, poor heat transfer; and poor reignition suppression. Because of their decreased efficiency, larger amounts of these substitute agents must be stored in fire suppression systems. This requirement for larger amounts of gaseous fire suppression agents increases the expense of the system and the space it occupies. Additionally, because of their relatively decreased fire suppression efficiency, more of these gaseous fire suppression agents must react with the flame to break the chain reaction of combustion and suppress the fire. Unfortunately, this increased reaction of gaseous fire suppression agents with the flame produces increased quantities of toxic and corrosive byproducts. Further, the cooling ability of many substitute gases is significantly less than that of Halon.TM.. Consequently, the risk of post suppression reignition increases.
Water mists have also been used for the suppression of compartment fires. While these system have reduced toxicity problems compared with gaseous fire suppression agents, they have several drawbacks. Because water mist does not behave completely like a gas, it may not reach all areas within a compartment. Thus, great care must be taken to assure that all areas within the compartment may be accessed by the spray. Also, water mist must be sprayed under extremely high pressures of about 250 psi or more. These pressures require specialized high pressure plumbing, thus increasing the expense of the system and limiting the ability to retrofit a previously existing compartment with a water mist system. Also, water mist systems require large amounts of water to extinguish a fire. The large weight and bulk of water, compared to gaseous fire suppression agents, makes storing the required large amounts of water troublesome. Because of these storage problems, designers may reduce the safety margin of these systems to minimize the amount of water that must be stored. Current systems which employ water and a gaseous propellant require high pressure and large amounts of both water and gaseous propellant.